Many games use a system that I like, where skills either increase in power over time, or you learn stronger versions of spells which replace your old ones. For damage spells, it's relatively simple - increase the coefficients and/or multipliers, and then compensate with a higher mp cost or cooldown. But for non-damage spells, it's more difficult: Take for example a barrier spell, which reduces physical damage taken. What's the weakest version of the spell that's still useful and not underpowered, and what's the strongest version of the spell that's powerful but not overpowered? I'm thinking the range to be something along the lines of.... Weakest version: 50% or 75% physical damage reduction for 1 to 2 turns, single target Strongest version: 75% physical damage reduction for 1 to 3 turns, entire party What would be the weakest version you'd still find balanced and useful, and the strongest version you'd find balanced but not broken?